Recovery of luminance and chrominance information from an encoded color television signal

Abstract

An apparatus and method for decoding an encoded video signal combs a two dimensional array of pixels from a single field of the encoded video signal according to selected weighting factors to obtain a weighted average chrominance value. The weighted average chrominance value is subtracted from the encoded value to obtain an initial luminance value. The initial luminance value is corrected for residual chrominance errors that exist at edges in the picture represented by the encoded video signal. The luminance correction is based upon the chorminance difference across the edge and upon the orientation of the edge. The corrected luminance value may then be subtracted from the corresponding encoded video value to obtain a corrected chrominance value.

What is claimed is: 
     
       1. A method for decoding the luminance and chrominance components for each pixel of an encoded video image comprising the steps of: obtaining a weighted average for the chrominance component of each pixel by combing vertically and horizontally over an array of pixels centered on the pixel being decoded, the array of pixels being selected from a single field of the encoded video image and from pixels having the same chrominance component; and   correcting the luminance component, obtained by subtracting the weighted average for the chrominance component from the encoded value for the pixel being decoded, as a function of a magnitude of chrominance change across an edge in the encoded video image and of the orientation of the edge.   
     
     
       2. A method as recited in claim 1 further comprising the step of subtracting the corrected luminance component from the encoded value for the pixel being decoded to obtain a corrected chrominance component. 
     
     
       3. A method as recited in claim 2 further comprising the steps of: detecting the edge in the encoded video image; and   selecting the corrected chrominance component when the edge is detected and the weighted average chrominance component when the edge is not detected.   
     
     
       4. An apparatus for decoding the luminance and chrominance components for each pixel of an encoded video image comprising: means for obtaining a weighted average for the chrominance component of each pixel by combing vertically and horizontally over an array of pixels centered on the pixel being decoded, the array of pixels being selected from a single field of the encoded video image; and   means for correcting the luminance component, obtained by subtracting the weighted average for the chrominance component from the encoded value for the pixel being decoded, as a function of a magnitude of chrominance change across an edge in the encoded video image and of the orientation of the edge.   
     
     
       5. An apparatus as recited in claim 4 further comprising means for subtracting the corrected luminance component from the encoded value for the pixel being decoded to obtain a corrected chrominance component. 
     
     
       6. An apparatus as recited in claim 5 further comprising: means for detecting the edge in the encoded video image; and   means for selecting the corrected chrominance component when the edge is detected and the weighted average chrominance component when the edge is not detected.